Homemade Nutella Cupcakes with Nutella filling

0 Start by Pre-heating your oven to 400 F and lining cupcake tins with cupcake liners. In a medium bowl, mix flour, cocoa powder, baking soda, baking powder, salt and set aside. 
1 Using a stand mixer with a paddle attachment, beat butter and sugar in a large bowl in medium speed until light and fluffy, about 1 1/2 minutes. Add eggs, one by one, beating after each addition. 
2 Add vanilla and sour cream and mix until combined. Alternate hot coffee and flour mixture, starting and finishing with dry ingredients and beating until well incorporated. Do not over mix.
3 Fill prepared cupcake tins 3/4 full with cupcake batter; bake for 5 minutes at 400 F, reduce temperature to 350 F and bake for an additional 10 minutes, or until a toothpick inserted in the middle comes out clean. Do not over bake to avoid cupcakes from becoming dry! Remove cupcakes from tins after 2 minutes and let them cool completely over a cooling rack before filling.
4 Using a melon baller, a pairing knife or a cupcake corer (see tips above), scoop or core the center of the cooled cupcakes and fill with Nutella using a piping bag. 
5 To make the Nutella buttercream, beat butter until creamy, about 1.5 minutes. Add Nutella and mix. Add powdered sugar, cocoa powder, cream, salt and vanilla extract. 
6 Beat on low speed until just incorporated, then beat in medium-high speed for 2 more minutes, until light and fluffy. Add more cream if needed.
7 Prepare a piping bag with your favoring piping tip. Use a butter knife to spread Nutella in a line on the side of the piping bag, from tip to end, then fill the piping bag with the Nutella buttercream. Pipe each cupcake with buttercream and top with crushed hazelnuts. Enjoy!